How many kids are vaccinated at your child's school? Federal health officials think you should be able to easily find out.

Last school year, only 21 states posted vaccination rates for individual schools, school districts, counties or areas of the state. The Centers for Disease Control and Prevention has been quietly prodding more states to make the information available online.

CDC's Dr. Anne Schuchat made the push more public during a press conference Thursday.

"It's important to recognize when vulnerabilities exist in communities," said Schuchat, who oversees the agency's vaccination work.

Parents could use the information to weigh their child's risk of vaccine-preventable illnesses at specific schools or school districts, Schuchat said. And it could help health officials identify pockets of unvaccinated children, she said.

All states require children to be vaccinated against certain infectious diseases like measles and polio before entering kindergarten. All states allow exemptions if there is a medical reason a child should not get a vaccine. Many states also allow exemptions for religious or philosophical reasons. Idaho has the highest proportion of kindergartners with exemptions, at 6.5 percent.

Some states have been trying to limit exemptions. After a measles outbreak, California this year dropped religious and philosophical exemptions for children at public and private schools.

Nationally, vaccination rates for both toddlers and kindergartners appear to be high and steady in recent years, at above 90 percent, according to two CDC reports released Thursday.___